Fluid pressurizing apparatus



March 1957 J. T. MARSHALL E 2,785,634

FLUID PRESSURIZING APPARATUS Filed Aug. is, 1950 2 Sheets-Sheet .1

INVEN w m4 y g m J M We m4 mmuk nrraP/vzr March 19-57 J. T. MARSHALL ETAL 2,785,634 FLUID PRESSURIZING APPARATUS 2 Sheets-Sheet 2 Filed Aug. 18, 1950 INVENTO. Y Jd/l/V awn-$14441:

ATTORNEY United States Patent FLUID PRESSURIZING APPARATUS John T. Marshall and Charles 0. Weisenbach, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application August 18, 1950, Serial No. 180,246

2 Claims. (Cl. 103-5) This invention relates to apparatus for pressurizing fuel for use in engines.

A principal object of the invention resides in the provision of a device capable of supplying fuel to an engine over a wide operating range.

An important object of the invention is to provide a pressurizing apparatus characterized by its absence of reciprocating parts and its simplicity in construction.

Another important object of the invention resides in the provision of a pressurizing apparatus having in combination, a first pump capable of pressurizing fuel to a predetermined value for supplying fuel to an engine during the starting period and a second pump having more desirable characteristics for pressurizing said fuel beyond said predetermined value for supplying fuel to the engine through the operating range.

A yet further important object of the invention resides in the provision of a turbine pump for pressurizing fuel to a predetermined value and a centrifugal pump carried by the same shaft as said turbine pump for further pressurizing the fuel delivered by said turbine pump.

A still further object of the invention resides in the provision of a pressurizing apparatus for use with an aircraft engine wherein a first pump maintains the inlet pressure to a second pump at a predetermined minimum value irrespective of altitude.

The above and other objects and features of the invention will be apparent from the following description of the apparatus taken in connection with the accompanying drawings which form a part of this specification, and in which:

Figurel is a diagrammatic representation of the pressurizing apparatus of the invention associated with a jet engine; and

Figure 2 is a longitudinal view in section through the axis of the pressurizing device.

Referring now to Figure 1, the reference numeral designates a nacelle in which a jet engine 12 is mounted. The engine is provided with a rotatable driving shaft 16 to which the pressurizing apparatus of the invention is connected. Fuel for the engine is received from a supply source, not shown, via conduit 18, pressurized by the apparatus 20, to be hereinafter described, and delivered through pipe line 22 to a manifold 24, from where the fuel is distributed to burners 26.

The pressurizing apparatus 20 of Figure 2 comprises a turbine pump 28 and a multi-stage centrifugal pump 30, both of which are mounted on a common drive shaft 32 connected to the engine shaft 16. The pumps are located in a sectionalized housing 34 held together by bolts 36.

The turbine pump is provided with vanes 37 secured to an impeller wheel 38, rotatably carried by the shaft 32, in a chamber 40. The liquid is pressurized in a channel 42 and discharged from outlet port 44 communicating with the channel 42. An inner annulus 46, formed from mating grooves in the housing and impeller wheel, communicates with suction or inlet, via passage 48, which terminates in a threaded opening 50, adapted to be connected to the conduit 18. Passages 52 and 54 provide communication between the inner annulus 46 and the channel 42. As observed in the drawing, Figure 2, it would seem that the suction or inlet is disposed nearly around the housing from the discharge port, but this showing is schematic only, and in actual practice would probably be different. Generally the suction and discharge ports are located adjacently in the housing, thus providing a comparatively long distance between the suction and discharge, to thereby develop maximum pressure at the discharge opening.

A relief valve 56 is interposed between the channel 42 and annulus 46 for preventing the turbine pump discharge pressure from exceeding a predetermined upper limit. This upper limit can be changed by adjusting nut 58 to vary the force of spring 60 interposed. between the nut and a valve member 62. The pressure in channel 42 acts on the face of the valve member 62 tending to move the same to the right against the aforesaid spring. The valve member is normally urged to the left to close ports 64 to prevent circulation between the channel 42 and the inner annulus 46, via the ports.

The discharge 44 of the turbine pump is connected to inlet or suction 66 of the two stage centrifugal pump 30. Fluid under pressure from the turbine pump is forced into the eye or center of the centrifugal pump, from Where it flows in between impeller vanes 68, of the impeller wheel 70, and under the action of centrifugal force the fluid is thrown outwardly into a volute channel 72. A passage 74 connects the volute 72 with eye 76 of the second stage centrifugal pump. Impeller wheel 78 draws fluid through the impeller vanes 80, and under the action of centrifugal force the fluid is thrown into volute channel 82. The volute channel 82 discharges into a passage 84, which communicates with the manifold 24, via the pipe line 22.

In addition to providing an engine driven apparatus which supplies fuel at a predetermined minimum pressure at all engine speeds, the apparatus has the advantage of high suction lift and decreasing power requirements as the operating head increases beyond said predetermined minimum pressure.

The turbine pump is connected anterior to the centrifugal pump inlet so that the inlet pressure is always maintained at some preselected value, depending upon the setting of the relief valve 56, to thereby'attenuate the tendency toward cavitation in the centrifugal pump.

Operation and function of the apparatus is as follows: Upon starting the engine the turbine pump, which is directly connected to the engine, begins circulating fuel through its vanes 37, thus building up pressure as the fuel flows from the suction to the discharge side of the pump. It will be noted that the starting apparatus for the engine, not shown, turns the shaft 16, and hence the pump, at a speed that is adequate for pressurizing the fuel for the engine fuel system, notwithstanding the slow shaft speed at this time compared to the normal idling speeds attained when the engine is running under its own power. The pressure head developed by the turbine pump forces fuel through the two stage centrifugal pump to the manifold 24, and thence to the burners 26. After the engine is started the centrifugal pump output pressure gradually increases with speed and becomes the primary source of pressure since the turbine pump is relieved at this point. This later pump has the advantage over the turbine pump in that the power requirements drop as the flow is re duced for any given speed.

After the pressure in the channel 42 has reached a predetermined value the relief valve 56 comes into action for bypassing the fuel to the annulus 46, to be recirculated, thus limiting the pump power requirements to a 3 predetermined maximum depending upon the pressure head. selected.,.

Although this invention has been described in connection With certain specific embodiments, the principles are susceptible of. numcrpus other applications that will readily occur to persons skilled in the art.

Having'thus described; the various features of. the. invention', Whatwe claim as new and. desire tosecur'e by Letters Patent is:

1. A pressurizing apparatus for supplying fluid to an engine comprising a shaft adapted to be engine driven,

a turbinefirst pump having an inlet and, an outlet mounted on said shaft, a centrifugal pump having an inlet and an outlet mounted on said shafu'a" connection from the outlet of said turbine pump to the inlet of said centrifugal pump, a bypass connecting the inlet andoutlet' of said turbine pump, and a'valve in said by-pass for, limiting said turbine pump discharge pressure.

2'. A liquid'pressurizing apparatus comprising a turbine first pump provided with inlet and discharge ports, a centrifugal pump, said pu'mps being driven from a common shaft, a fiuid passage connecting the discharge port of the, turbine pump to the inlet side of the centrifugal pump, a conduit connecting the inlet and outlet of said turbine pump, a valve in" said conduit adapted to be opened at a predetermined turbine discharge pressure, and a resilient means urging said valve in a closing direction.

References Cited inthe file of this patent "'UfiiTE'D STATES PATENTS an .1 P 

